This invention relates to a marine engine exhaust muffler assembly and more particularly to a muffler for use in association with an inboard marine engine.
Over the years, stern drive engines have become more and more powerful, with an accompanying increase in noise levels due to exhaust discharge and flow noise. Such noise needs to be reduced as much as possible, both for the comfort of the user and also to accommodate restrictions on overall noise levels imposed by various environmental pollution control agencies.
It is an object of the present invention to provide a marine engine exhaust muffler which effectively reduces related noise levels and which is relatively simple in construction and economical to manufacture. It is a further object to provide a muffler which can easily be retrofit to most stern drive marine engine systems.
In accordance with the various aspects of the invention, a muffler assembly includes inlet and outlet members, the axes of which are offset from each other. A muffler housing is disposed between the inlet and outlet members and forms a chamber having disposed therein an annular multi-layered cartridge, and with the layers having a multiplicity of perforations therein for passage of exhaust gases and spent engine cooling water therethrough. The water assists in keeping the muffler clean. An imperforate arcuate blocking plate is nested within the lower portion of the cartridge to permit accumulation of the spent engine cooling water within the cartridge to aid in noise reduction at certain engine speeds. The blocking plate is provided with a relief opening means for assisting in water drainage upon engine shutoff.